v=[1 0]';
c=[-3:1:3];
p=v*c;

subplot(131)
plot(p(1,:),p(2,:),'o')
grid on
axis square
axis([-3 3 -3 3])
text(0.2,0.2,'S_1')

subplot(132)
plot([0 3],[0 0],'b','LineWidth',2)
grid on
axis square
axis([-3 3 -3 3])
text(0.2,0.2,'S_2')

subplot(133)
plot([-3 3],[0 0],'b','LineWidth',2)
grid on
axis square
axis([-3 3 -3 3])
text(0.2,0.2,'S_3')

